Reversible flow valve assembly

ABSTRACT

A valve is provided that comprises a valve chamber including first and second valve port openings in communication with first and second inlet/outlets, respectively. A shaft is rotatably disposed in the valve chamber. A first valve plate is rotatably coupled to the shaft that is disposed in the valve chamber over the first valve port opening. The first valve plate has a first opening positioned so as to align with the first valve port opening. The first valve plate is configured to rotate from its closed position covering the first valve port opening to an open position, where rotation of the first valve plate adjustably positions at least a portion of the first opening over the first valve port opening. A second valve plate is configured to rotate with the first valve plate, and to cover the second valve port opening.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/472,931 filed May 27, 2009, which issues Dec. 13, 2011 as U.S. Pat.No. 8,074,678. The entire disclosure of the above application isincorporated herein by reference.

FIELD

The present disclosure relates to flow control valves, and moreparticularly to motor actuated modulating flow control valves.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

In a conventional refrigeration or HVAC system, flow control devices aretypically utilized to control the flow of working fluids in arefrigeration system. In general, the refrigeration system would includea compressor that forces the particular refrigerant used in the systemthrough a condensing coil, where the refrigerant vapor liquefies. Theliquid refrigerant passes through a thermostatic expansion valve,expanding the high pressure liquid refrigerant to a low pressure vapor.The low pressure, low temperature refrigerant discharged from thethermostatic expansion valve is then directed through an evaporator coilfor absorbing heat and thus refrigerating the space inside the containersurrounding the evaporator coil.

The thermostatic expansion valve functions to meter the flow ofrefrigerant into the evaporator coil in proportion to the rate ofevaporation of the refrigerant in the evaporator coil, and is responsiveto the temperature and pressure of the refrigerant leaving theevaporator coil. In this manner, the thermostatic expansion valve isintended to control flow so that the refrigerant leaves the evaporatorcoil at a predetermined superheat. Generally, the superheat of therefrigerant is a measure of the heat contained in the refrigerant vaporabove its heat content at the boiling point (saturated vaportemperature) at the existing pressure. Maintaining the refrigerantentering the suction line from the evaporator coil at a desiredsuperheat level enhances the refrigeration system performance.

Thermal expansion valves are typically used, in conjunction with asuction regulator, to maintain a consistent evaporator coil pressure. Inknown systems, conventionally designed mechanical pressure regulatorsare used for this purpose. Conventional mechanical pressure regulatorsinclude a throttling element that, when moved, limits the flow of therefrigerant through the suction regulator to regulate the pressure. Adiaphragm, or other sensing element, responds to variations in the inletpressure and moves the throttling element accordingly. A referencepressure, typically exerted by a spring, is applied to one side of thediaphragm to bias the diaphragm in a desired position, or set point.High side inlet pressure is applied to the other side of the diaphragmto move the diaphragm against the spring, and thus, move the throttlingelement.

In many refrigeration system implementations, finer temperature controlis desirable. Adjusting the setting of conventionally designedmechanical pressure regulators in such thermal expansion valves can be atime consuming, manual process. Moreover, if the refrigerant or desiredtemperature changes, the complicated process of manually adjusting thepressure regulator's set screw must be repeated.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present disclosure relates to various embodiments of a reversibleflow expansion valves. In an exemplary embodiment, a valve generallyincludes a valve chamber including first and second valve port openingsin communication with first and second inlet/outlets, respectively. Ashaft is rotatably disposed in the valve chamber. A first valve plate isrotatably coupled to the shaft that is disposed in the valve chamberover the first valve port opening. The first valve plate has a firstopening positioned so as to align with the first valve port opening. Thefirst valve plate is configured to rotate from its closed positioncovering the first valve port opening to an open position, whererotation of the first valve plate adjustably positions at least aportion of the first opening over the first valve port opening. A secondvalve plate is configured to rotate with the first valve plate, and tocover the second valve port opening.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure in any way.

FIG. 1 is a cross-sectional perspective view of a first embodiment of areversible flow expansion valve shown in a closed position, inaccordance with the principles of the present disclosure;

FIG. 2 is a cross-sectional lower perspective view of the reversibleflow expansion valve shown in FIG. 1;

FIG. 3 is a front perspective view of the reversible flow expansionvalve shown in FIG. 1, without the stepper motor;

FIG. 4 is a cross-sectional side view of the reversible flow expansionvalve shown in FIG. 3;

FIG. 5 is a top elevation view of the reversible flow expansion valveshown in FIG. 3, without the rotor of the stepper motor;

FIGS. 6A-6D are top elevation views of the reversible flow expansionvalve shown in FIG. 5, illustrating various rotational positions of thevalve plates;

FIG. 7 is another cross-sectional perspective view of the reversibleflow expansion valve shown in FIG. 1;

FIG. 8 is a cross-sectional side view of the reversible flow expansionvalve shown in FIG. 1 with an outer valve plate elevated;

FIG. 9 is a perspective view of the inner and outer valve plates of thevalve shown in FIG. 1, with an outer valve plate elevated;

FIG. 10 is a cross-sectional perspective view of the reversible flowexpansion valve shown in FIG. 1 with an outer valve plate elevated;

FIG. 11 is a cross-sectional side view of the reversible flow expansionvalve shown in FIG. 1 with an inner valve plate elevated;

FIG. 12 is a perspective view of the inner and outer valve plates of thevalve shown in FIG. 1, with an inner valve plate elevated;

FIG. 13 is a cross-sectional perspective view of the reversible flowexpansion valve shown in FIG. 1 with an inner valve plate elevated;

FIG. 14 is a cross-sectional perspective view of a second embodiment ofa reversible flow expansion valve shown in a closed position, inaccordance with the principles of the present disclosure;

FIG. 15 is a perspective view of the first and second valve disks of thereversible flow expansion valve shown in FIG. 14;

FIG. 16 is a cross-sectional side view of the reversible flow expansionvalve shown in FIG. 14 with a first valve disk elevated; and

FIG. 17 is a cross-sectional side view of the reversible flow expansionvalve shown in FIG. 14 with a second valve disk elevated.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

According to various aspects of the present disclosure, there areprovided various exemplary embodiments of a reversible flow expansionvalve. In the various embodiments, a reversible flow expansion valve isprovided that comprises a valve housing having a valve chamber includinga first valve port opening and a second valve port opening incommunication with a first inlet/outlet and a second inlet/outlet of thevalve, respectively. The various embodiments further include a shaftrotatably disposed in the valve chamber. A first valve plate is disposedin the valve chamber over the first valve port opening, and is rotatablycoupled to the shaft. The first valve plate has a first taperedsemi-circular slot positioned in the first valve plate so as to alignwith the first valve port opening. The first valve plate is configuredto rotate from a closed position, in which the first valve plate ispositioned over the first valve port opening, to an open position inwhich rotation of the first valve plate adjustably positions a wider ornarrower portion of the first tapered semi-circular slot over the firstvalve port opening. This adjustably varies the rate of fluid flowthrough the first valve port opening. The first valve plate in itsclosed position is also configured to be movable in an axial directiontowards and away from the first valve port opening. The variousembodiments further include a second valve plate that is configured torotate with the first valve plate, and is positioned over the secondvalve port opening when the first valve plate is rotated to the closedposition. The second valve plate is also configured to be movablerelative to the first valve plate, in an axial direction towards andaway from the second valve port opening.

In another aspect of the various embodiments, the first valve plate inits closed position is configured to move away from the first valve portopening, and the second valve plate in the closed position is configuredto move against the second valve port opening, to thereby resist fluidflow through the second valve port opening. Likewise, the second valveplate in its closed position is configured to move away from the secondvalve port opening, and the first valve plate in the closed position isconfigured to move against the first valve port opening, to therebyresist fluid flow through the first valve port opening.

Referring to FIG. 1, a first embodiment of a reversible flow expansionvalve is shown generally at 100. The reversible flow expansion valve 100comprises a valve housing 106 having a first inlet/outlet 102 and asecond inlet/outlet 104 that are configured for fluid flow in eitherdirection. The reversible flow expansion valve 100 further includes avalve chamber 110 having a lower wall 108 therein.

As shown in FIG. 2, the lower wall 108 of the valve chamber 110 has afirst valve port opening 112 in communication with the firstinlet/outlet 102, and a second valve port opening 114 in communicationwith the second inlet/outlet 104. A shaft 144 is rotatably disposed inthe valve chamber 110 in a generally vertical or perpendicularorientation relative to the lower wall 108. The shaft 144 may furtherinclude a rotor 146, which may be coupled to the shaft 144, oralternatively, integrally formed with the shaft 144.

An inner modulating disk 120 (or plate) is rotatably coupled to theshaft 144. Although the inner modulating plate shown in the variousfigures has a generally round disk-shape, it should be noted that thevarious plates disclosed herein may alternatively comprise a shape otherthan that of a disk. As shown in FIG. 2, the inner modulating disk 120is disposed in the valve chamber 110 over the first valve port opening112, and is generally positioned against the lower wall 108 of the valvechamber 110.

Referring to FIGS. 4-6, the inner modulating disk 120 has a firsttapered semi-circular slot 122 that is aligned with the first valve portopening 112 (see FIG. 5). The inner modulating disk 120 is configured torotate from a closed position, in which the inner modulating disk 120 ispositioned over the first valve port opening 112 (shown in FIGS. 4 and6A), to an open position in which rotation of the inner modulating disk120 adjustably positions a wider or narrower portion of the firsttapered semi-circular slot 122 over the first valve port opening 112(shown in FIGS. 6B-6D). The positioning of a wider or narrower portionof the first tapered semi-circular slot 122 over the first valve portopening 112 provides for adjustably varying the rate of fluid flowthrough the first valve port opening 112. As shown in FIG. 7, the innermodulating disk 120 is configured to rotate about its center, by virtueof a central aperture 121 having a keyed configuration, where rotationof the inner modulating disk 120 positions a portion of the firsttapered semi-circular slot 122 over the first valve port opening 112.

Referring to FIG. 8, the inner modulating disk 120 in its closedposition is further configured to be pushed against the first valve portopening 112 by a fluid pressure in the valve chamber 110 that is greaterthan the fluid pressure in the first valve port opening 112. Thisdifferential pressure above and below the inner modulating disk resultsin a downward force being applied, such that the inner modulating disk120 sealingly engages the first valve port opening 112 and therebyresists fluid flow through the first valve port opening 112. The innermodulating disk 120 also includes a slot 123 that is configured to becoupled with a mating keyed-portion 125 of an outer modulating disk 126as shown in FIG. 9, which will be described below.

The reversible flow expansion valve 100 shown in FIG. 7 furthercomprises the outer modulating disk 126 encircling the inner modulatingdisk 120. The outer modulating disk 126 is disposed in the valve chamber110 over the second valve port opening 114. The outer modulating disk126 has a second tapered semi-circular slot 124 that is aligned with thesecond valve port opening 114 (see FIG. 5). The outer modulating disk126 is coupled to and configured to rotate with the inner modulatingdisk 120. The outer modulating disk 126 rotates from a closed position,in which the outer modulating disk 126 is positioned over the secondvalve port opening 114 (as shown in FIGS. 4, 7, and 11), to an openposition in which rotation of the outer modulating disk 126 adjustablypositions a wider or narrower portion of the second taperedsemi-circular slot 124 over the second valve port opening 114 (as shownin FIG. 6B-6D). The positioning of a wider or narrower portion of thesecond tapered semi-circular slot 124 over the second valve port opening114 provides for adjustably varying the rate of fluid flow through thesecond valve port opening 114. Accordingly, rotation of the innermodulating disk 120 (and outer modulating disk 126 encircling the innermodulating disk 120) adjustably positions a wider or narrower portion ofboth the first tapered semi-circular slot 122 and second taperedsemi-circular slot 124 over the first valve port opening 112 and secondvalve port opening 114 respectively, to adjustably vary the rate offluid flow through the valve 100.

The outer modulating disk 126 is further configured to be axiallymovable in a direction towards and away from the second valve portopening 114. Referring to FIG. 10, the outer modulating disk 126 in itsclosed position is also configured to be pushed against the second valveport opening 114 by a fluid pressure in the valve chamber 110 that isgreater than the fluid pressure in the second valve port opening 114,such that the outer modulating disk 126 sealingly engages the secondvalve port opening 114 to thereby resist fluid flow through the secondvalve port opening 114.

Referring to FIG. 9, the inner modulating disk 120 in the firstembodiment preferably comprises a plate having a generally round contouror periphery, a central aperture 121 having a keyed configuration orsurface with which the inner modulating disk 120 may be rotated, and afirst tapered semi-circular slot 122 that is concentric with the centralaperture 121. The first tapered semi-circular slot 122 may becomet-shaped or semi-circular in contour, and generally partiallyencircles or surrounds the central aperture 121 in a concentric manner(as shown in FIG. 5, for example). The outer modulating disk 126comprises a plate having a generally ring-shaped contour and a secondtapered semi-circular slot 124 that is concentric with the first taperedsemi-circular slot 122. The second tapered semi-circular slot 124 mayalso be comet-shaped or semi-circular in contour, and generallypartially encircles or surrounds the central aperture 121 in aconcentric manner (as shown in FIG. 5, for example). The inner and outermodulating disks 120, 126 are coupled to each other such that the firstand second tapered semi-circular slots 122, 124 are disposed ongenerally opposing sides of the central aperture 121. The first andsecond tapered semi-circular slots 122, 124 are generally disposed ongenerally opposing sides of the central aperture 121 of the innermodulating disk 120, to correspondingly align with the first and secondvalve port openings 112 and 114 that are also on generally opposed sidesof the valve chamber 110.

It should be noted that the valve may comprise an alternativeconstruction in which the first tapered semi-circular slot 122 andsecond tapered semi-circular slot 124 are positioned on the same side ofthe central aperture 121 (as opposed to opposite sides), and the firstand second valve port openings 112, 114 are likewise positioned on thesame side of the valve chamber 110. Accordingly, the first and secondinner and outer modulating disks 120, 126 may have a first taperedsemi-circular slot 122 and second tapered semi-circular slot 124 in anyarrangement that corresponds to the orientation of the first and secondvalve port openings 112, 114 within the valve chamber 110.

As shown in FIG. 7, the inner modulating disk 120 and outer modulatingdisk 126 are configured to be rotated to a substantially closedposition, in which the inner modulating disk 120 is positioned over thefirst valve port opening 112, and the outer modulating disk 126 ispositioned over the second valve port opening 114. In yet another aspectof the present disclosure, the inner modulating disk 120 and outermodulating disk 126 are further configured to be movable towards andaway from their respective valve port openings. Specifically, the shaft144 is configured to be movable in an axial direction such that theinner modulating disk 120 coupled to the shaft 144 is movable in adirection towards and away from the first valve port opening 112. Theshaft 144 may further be biased by a first spring 130. As previouslystated, the inner modulating disk 120 is coupled to the outer modulatingdisk 126 by a key 125 and slot 123 arrangement that permits the outermodulating disk 126 to move axially (relative to the inner modulatingdisk 120) toward and away from the second valve port opening 114, asexplained below.

The inner modulating disk 120 in its closed position is positioned overthe first valve port opening 112, and is configured to be moved againstthe first valve port opening 112 by a fluid pressure in the valvechamber 110 above the inner modulating disk 120 that is greater than thefluid pressure in the first valve port opening 112 below the innermodulating disk 120. This higher pressure above the inner modulatingdisk 120 results in a downward force being applied, such that the innermodulating disk 120 sealingly engages the first valve port opening 112and thereby resists fluid flow through the first valve port opening 112.The outer modulating disk 126 in its closed position is positioned overthe second valve port opening 114, and is configured to be moved againstthe second valve port opening 114 by a fluid pressure in the valvechamber 110 above the outer modulating disk 126 that is greater than thefluid pressure in the second valve port opening 114 below the outermodulating disk 126. This higher pressure above the outer modulatingdisk 126 results in a downward force being applied, such that the outermodulating disk 126 sealingly engages the second valve port opening 114,to thereby resist fluid flow through the second valve port opening 114.Accordingly, the inner and outer modulating disks 120, 126 areconfigured to move axially towards their respective valve port openings,such that a pressure in the valve chamber 110 that is higher than thepressure below a given modulating disk will provide for effectivelysealing the disk against its respective valve port opening.

Referring to FIGS. 8-10, the inner modulating disk 120 and outermodulating disk 126 (in the closed position) are each configured to moveaxially away from their respective valve port openings 112, 114 whenfluid pressure below the first or second inner or outer modulating disks120, 126 is higher than the pressure in the valve chamber 110. A fluidpressure in the second valve port opening 114 that is higher than fluidpressure in the valve chamber 110 causes the outer modulating disk 126in its closed position to move relative to the inner modulating disk 120(see FIG. 9) in an axial direction away from the second valve portopening 114 (see FIG. 8). This permits communication of fluid pressureto the valve chamber 110 (see FIG. 10), which establishes a higherpressure in the valve chamber 110 than in the first valve port opening112. A fluid pressure in the first valve port opening 112 that is lowerthan fluid pressure in the valve chamber 110 causes the inner modulatingdisk 120 (which is axially movable with the shaft 144) to move againstthe first valve port opening 112, and thereby establish a seal againstthe first valve port opening 112.

Referring to FIGS. 11-13, the inner modulating disk 120 (in the closedposition) is also configured to move axially away from the first valveport opening 112 when fluid pressure below the inner modulating disk 120is higher than the pressure in the valve chamber 110. A fluid pressurein the first valve port opening 112 that is higher than fluid pressurein the valve chamber 110 causes the inner modulating disk 120 in itsclosed position to move relative to the outer modulating disk 126 (seeFIG. 12) in an axial direction away from the first valve port opening112. This permits fluid flow into the valve chamber 110 (see FIG. 13),which establishes a higher pressure in the valve chamber 110 than in thesecond valve port opening 114. A fluid pressure in the second valve portopening 114 that is lower than fluid pressure in the valve chamber 110causes the outer modulating disk 126 (which is axially movable relativeto the inner modulating disk 120) to move against the second valve portopening 114, and thereby establish a seal against the second valve portopening 114. Thus, the inner modulating disk 120 and outer modulatingdisk 126 are configured to move away from their respective valve portopenings where there is an uneven pressure between the firstinlet/outlet 102 and the second inlet/outlet 104 of the valve 100, asexplained below.

In the first embodiment of a reversible flow expansion valve, unevenpressures at the first inlet/outlet 102 and the second inlet/outlet 104can act against the first and second modulating disks 120, 126 in theirclosed positions. To counteract this, the reversible flow expansionvalve 100 includes a second biasing spring 132 for biasing the innermodulating disk 120 towards the first valve port opening 112. The innermodulating disk 120 in its closed position is configured to be movedaway from the first valve port opening 112 (against the force of thesecond biasing spring 132) by fluid pressure in the first valve portopening 112 that is greater than fluid pressure in the valve chamber 110(e.g., fluid pressure at the first inlet/outlet 102 and the valvechamber 110 is higher than the pressure at the second inlet/outlet 104).Thus, fluid pressure in the first valve port opening 114 that is higherthan fluid pressure in the valve chamber 110 causes the inner modulatingdisk 120 in its closed position to move in an axial direction away fromthe first valve port opening 112. This permits communication of fluidpressure via bleed chamber 184 to the valve chamber 110, which, in turn,pushes the outer modulating disk 126 against the second valve portopening 114 (see FIG. 13). The outer modulating disk 126 in its closedposition is also configured to be moved away from the second valve portopening 114 by a fluid pressure in the second valve port opening 114that is greater than fluid pressure in the valve chamber 110 (e.g.,fluid pressure at the second inlet/outlet 104 and the valve chamber 110is higher than the pressure at the first inlet/outlet 102). Thus, fluidpressure in the second valve port opening 114 that is higher than fluidpressure in the valve chamber 110 causes the outer modulating disk 126in its closed position to move in an axial direction away from thesecond valve port opening 114.

Movement of the first or inner modulating disk 120 away from the valveport opening 112 establishes communication of fluid pressure to thevalve chamber 110 via a bleed passage 182 between the lower wall 108 anddisk 120 as shown in FIG. 10. Movement of the second or outer modulatingdisk 126 away from the valve port opening 114 establishes communicationof fluid pressure to the valve chamber 110 via a bleed passage 184between the lower wall 108 and disk 126 as shown in FIG. 11. The bleedpassages 182, 184 allow for communication of higher fluid pressure tothe valve chamber 110, which, in turn, applies a force against the diskcovering a valve port opening that is at a lower pressure, to therebyprovide an improved seal.

The reversible flow expansion valve 100 may further include a motor 140(see FIG. 1) for rotating the shaft 144 that is coupled to the innermodulating disk 120 via the central aperture 121, for effecting rotationof the inner and outer modulating disks 120, 126. The motor 140controllably rotates the inner and outer modulating disks 120, 126 toincrementally index the first and second tapered semi-circular slots122, 124 to a plurality of angular positions (see FIG. 6B-6D) forincrementally adjusting the rate of fluid flow through the first andsecond valve port openings 112, 114 and the valve 100. It should benoted that in the first embodiment, the motor 140 is preferablyconfigured to hold its angular orientation and the position of the innerand outer modulating disks 120, 126 in the closed position relative tothe valve port openings in the valve housing 106, so that the inner andouter modulating disks 120, 126 are continuously covering the valve portopenings 112 and 114.

It should be appreciated from the above, that rotation of the inner andouter modulating disks 120, 126 adjustably positions a wider or narrowerportion of both the first and second tapered semi-circular slots 122,124 over the first and second valve port openings 112, 114,respectively, to adjustably vary the rate of fluid flow through thevalve 100. Furthermore, the movement of inner and outer modulating disks120, 126 relative to the first and second valve port openings 112, 114allows for establishing an improved seal against the first and secondvalve port openings 112, 114, to provide a check valve feature foraddressing differential or uneven pressures between the firstinlet/outlet 102 and the second inlet/outlet 104 (such as a pressuredifferential of at least 5 pounds per square inch (psi)). Thus, theinner and outer modulating disks 120, 126 of the first embodimentprovide for varying the fluid flow rate through the valve, and alsoprovide for improved closure in either flow direction against the valveport opening that is at a lower pressure.

Referring to FIG. 14, a second embodiment of a reversible flow expansionvalve 200 is shown. The second embodiment 200 functions similarly tothat of the first embodiment. However, unlike the tapered semi-circularslots in the first embodiment that are respectively disposed in separateinner and outer modulating disks (120, 126), the first and secondtapered semi-circular slots in the second embodiment are both disposedin an integrally formed first modulating disk in which a smaller,separate axially movable disk is disposed, as will be explained below.

The second embodiment of a reversible flow expansion valve 200 comprisesa valve housing 206 having a first inlet/outlet 202 and a secondinlet/outlet 204 configured for fluid flow in either direction. Thereversible flow expansion valve 200 further includes a valve chamber 210having a lower wall 208 therein. As shown in FIG. 14, the lower wall 208of the valve chamber 210 has a first valve port opening 212 incommunication with the first inlet/outlet 202, and a second valve portopening 214 in communication with the second inlet/outlet 204. A shaft244 is rotatably disposed in the valve chamber 210 in a generallyvertical or perpendicular orientation relative to the lower wall 208.The shaft 244 may further include a rotor 246, which may be eithercoupled to the shaft 244 or integrally formed with the shaft 244.

A first modulating disk 220 (or plate) is rotatably coupled to the shaft244. Although the first modulating plate shown in FIGS. 14-17 has agenerally round disk-shape, it should be noted that the modulating platemay alternatively comprise a shape other than that of a disk. As shownin FIG. 14, the first modulating disk 220 is disposed in the valvechamber 210 over the first valve port opening 212, and is generallypositioned against the lower wall 208 of the valve chamber 210. Thefirst modulating disk 220 has a first tapered semi-circular slot 222that is aligned with the first valve port opening 212, and has a secondtapered semi-circular slot 224 that is aligned with the second valveport opening 214. The first modulating disk 220 is configured to rotateabout its center, by virtue of a central aperture 221 having a keyedconfiguration. The first modulating disk 220 is configured to rotatefrom a closed position, in which the first modulating disk 220 ispositioned over the first valve port opening 212, to an open position,in which the first and second tapered semi-circular slots 222, 224 arepositioned over the first and second valve port openings 212, 214.Similar to the various positions shown in FIGS. 6B-6D, the firstmodulating disk 220 may be rotated to varying angles, to adjustablyposition a wider or narrower portion of the first tapered semi-circularslot 222 over the first valve port opening 212, and a wider or narrowerportion of the second tapered semi-circular slot 224 over the secondvalve port opening 214. The positioning of a wider or narrower portionof the first and second tapered semi-circular slots 222, 224 over thefirst and second valve port openings 212, 214 provides for adjustablyvarying the rate of fluid flow through the first and second valve portopenings 212, 214 (and thereby the valve).

Referring to FIG. 15, the first modulating disk 220 preferably comprisesa plate having a generally round contour or periphery, a centralaperture 221 having a keyed configuration or surface with which thefirst modulating disk 220 may be rotated. The first modulating disk 220has a first tapered semi-circular slot 222 that is concentric with thecentral aperture 221, and a second tapered semi-circular slot 224 thatis concentric with the first tapered semi-circular slot 222. The firsttapered semi-circular slot 222 may be comet-shaped or semi-circular incontour, and generally partially encircles or is concentric to thecentral aperture 221 (as shown in FIG. 15). The first modulating disk220 further comprises a second tapered semi-circular slot 224 that isalso comet-shaped or semi-circular in contour, and generally partiallyencircles or is concentric to the central aperture 221. The first andsecond tapered semi-circular slots 222, 224 are disposed on generallyopposing sides of the central aperture 221 of the first modulating disk220, to correspondingly align with the first and second valve portopenings 212 and 214 that are also on generally opposed sides of thevalve chamber 210. The first and second tapered semi-circular slots 222,224 are aligned or positioned to correspond with the position of thefirst and second valve port openings 212 and 214, such that rotation ofthe first modulating disk 220 adjustably positions a wider or narrowerportion of both the first tapered semi-circular slot 222 and secondtapered semi-circular slot 224 over the first valve port opening 212 andsecond valve port opening 214 respectively.

It should be noted that the valve may comprise an alternativeconstruction in which the first tapered semi-circular slot 222 andsecond tapered semi-circular slot 224 are positioned on the same side ofthe central aperture 221 (as opposed to opposite sides), and the firstand second valve port openings 212, 214 are likewise positioned on thesame side of the valve chamber 210. Accordingly, the first modulatingdisk 220 may have a first tapered semi-circular slot 222 and secondtapered semi-circular slot 224 in any arrangement that corresponds tothe orientation of the first and second valve port openings 212, 214within the valve chamber 210.

Referring to FIG. 16, the first modulating disk 220 is furtherconfigured to be rotated to a closed position, in which the firstmodulating disk 220 is positioned over the first valve port opening 212,and the valve port opening 214 is covered by a secondpressure-responsive disk 226 (which will be described below). The firstmodulating disk 220 in its closed position is further configured to bepushed against the first valve port opening 212 by a fluid pressure inthe valve chamber 210 that is greater than the fluid pressure in thefirst valve port opening 212. This higher pressure above the firstmodulating disk 220 results in a downward force being applied, such thatthe first modulating disk 220 sealingly engages the first valve portopening 212 and thereby resists fluid flow through the first valve portopening 212. The first modulating disk 220 also includes a cavity 223therein that is configured to receive a second pressure-responsive diskor member 226.

The reversible flow expansion valve 200 shown in FIGS. 14-17 furthercomprises a second pressure-responsive disk 226 disposed within thecavity 223 in the first modulating disk 220. The secondpressure-responsive disk 226 comprises a plate having a generallydisk-shaped contour, and a generally convex top surface 228 thatcorresponds to the surface contour of the cavity 223 in the firstmodulating disk 220. The second pressure-responsive disk 226 is confinedbetween the cavity 223 and lower wall 208, such that it is configured torotate with the first modulating disk 220. The secondpressure-responsive disk 226 is smaller than the cavity 223 of the firstmodulating disk 220, such that the second pressure-responsive disk 226is disposed within the cavity 223 in a floating manner that permits thesecond pressure-responsive disk 226 to move axially relative to thefirst modulating disk 220.

As shown in FIG. 16, when the first modulating disk 220 is rotated tothe closed position, the second pressure-responsive disk 226 within thecavity 223 is aligned with or positioned over the second valve portopening 214. When positioned over the second valve port opening 214, thesecond pressure-responsive disk 226 is configured to be pushed againstthe second valve port opening 214 by a fluid pressure in the valvechamber 210 that is greater than the fluid pressure in the second valveport opening 214. This higher pressure above the secondpressure-responsive disk 226 results in a downward force being applied,such that the second pressure-responsive disk 226 sealingly engages thesecond valve port opening 214, to thereby resist fluid flow through thesecond valve port opening 214. Accordingly, the first and second disks220, 226 are configured to move axially towards their respective valveport openings, such that a pressure in the valve chamber 210 that ishigher than the pressure below a given modulating disk will provide foran effective seal between the disk and valve port opening.

In yet another aspect of the present disclosure, the first modulatingdisk 220 or second pressure-responsive disk 226 (in the closed position)are further configured to move axially away from their respective valveport openings 212, 214 when fluid pressure below the first or seconddisk 220, 226 is higher than the pressure in the valve chamber 210.Specifically, the shaft 244 is configured to be movable in an axialdirection such that the first modulating disk 220 coupled to the shaft244 is movable in a direction towards and away from the first valve portopening 212. As shown in FIG. 16, a fluid pressure in the first valveport opening 212 that is higher than fluid pressure in the valve chamber210 causes the first modulating disk 220 in its closed position to movein an axial direction away from the first valve port opening 212. Thispermits communication of fluid pressure to the valve chamber 210 viapassage 282 (see FIG. 16), which establishes a higher pressure in thevalve chamber 210 than in the second valve port opening 214. Fluidpressure in the second valve port opening 214 that is lower than fluidpressure in the valve chamber 210 causes the second pressure-responsivedisk 226 (which is movable within the cavity 223 in the first modulatingdisk 220) to move against the second valve port opening 214, and therebyestablish a seal against the second valve port opening 214.

Likewise, the second pressure-responsive disk 226 is configured to bemovable within the cavity 223 in the first modulating disk 220 in anaxial direction away from the second valve port opening 214, as shown inFIG. 17. Fluid pressure in the second valve port opening 214 that ishigher than fluid pressure in the valve chamber 210 causes the secondpressure-responsive disk 226 in its closed position to move in an axialdirection away from the second valve port opening 214. This permitscommunication of fluid pressure to the valve chamber 210 via passage 284(see FIG. 17), which establishes a higher pressure in the valve chamber210 than in the first valve port opening 212. Fluid pressure in thefirst valve port opening 212 that is lower than fluid pressure in thevalve chamber 210 causes the first modulating disk 220 in its closedposition to move in an axial direction against the first valve portopening 212. Thus, the first modulating disk 220 and secondpressure-responsive disk 226 are configured to move away from theirrespective valve port openings where there is an uneven pressure betweenthe first inlet/outlet 202 and the second inlet/outlet 204 of the valve200, as explained below.

In the second embodiment of a reversible flow expansion valve 200,uneven pressures at the first inlet/outlet 202 and the secondinlet/outlet 204 can act against the first and second disks 220, 226 intheir closed positions. To counteract this, the reversible flowexpansion valve 200 includes a biasing spring 232 for biasing the firstmodulating disk 220 towards the first valve port opening 212. The firstmodulating disk 220 in its closed position is configured to be movedaway from the first valve port opening 212 (against the force of thebiasing spring 232) by fluid pressure in the first valve port opening212 that is greater than fluid pressure in the valve chamber 210 (e.g.,fluid pressure at the first inlet/outlet 202 and the valve chamber 210is higher than the pressure at the second inlet/outlet 204). Thus, fluidpressure in the first valve port opening 212 that is higher than fluidpressure in the valve chamber 210 causes the first modulating disk 220in its closed position to move in an axial direction away from the firstvalve port opening 212. The second pressure-responsive disk 226 in itsclosed position is also configured to be moved away from the secondvalve port opening 214 by fluid pressure in the second valve portopening 214 that is greater than fluid pressure in the valve chamber 210(e.g., fluid pressure at the second inlet/outlet 204 and the valvechamber 210 is higher than the pressure at the first inlet/outlet 202).Thus, fluid pressure in the second valve port opening 214 that is higherthan fluid pressure in the valve chamber 210 causes the secondpressure-responsive disk 226 in its closed position to move in an axialdirection away from the second valve port opening 214.

The movement of either the first or second disk 220, 226 away from itsrespective valve port opening establishes communication of fluidpressure to the valve chamber 210 via a bleed passage 282, 284 betweenthe lower wall 208 and disk. The bleed passages 282, 284 allow forcommunication of higher fluid pressure to the valve chamber 210, which,in turn, applies a force against the disk covering a valve port openingthat is at a lower pressure, to thereby provide an improved seal betweenthe disk and valve port opening.

Accordingly, the movement of first and second disks relative to thefirst and second valve port openings allows for establishing an improvedseal against the first and second valve port openings, to provide acheck valve feature for addressing differential or uneven pressuresbetween one inlet/outlet and the other inlet/outlet (such as a pressuredifferential across the inlet and outlet of at least 5 psi). Adifferential or uneven pressure between the valve inlet and outlet wouldtend to subject the valve chamber to a higher pressure than the outlet,which could result in fluid leakage when the valve is in a closedposition. The present design counteracts any uneven pressure situationby utilizing the higher fluid pressure in the valve chamber to establisha tight seal between the first or second pressure-responsive disk andits associated valve port opening in which fluid pressure is lower thanthe pressure in the valve chamber.

The reversible flow expansion valve 200 may further include a steppermotor rotor 246 connected to the shaft 244 that is coupled to the firstmodulating disk 220 via the central aperture 221, for effecting rotationof the first modulating disk 220. The rotor 246 controllably rotates thefirst and second disks 220, 226 to incrementally index the first andsecond tapered semi-circular slots 222, 224 to a plurality of angularpositions (similar to that shown in FIG. 6B-6D) for incrementallyadjusting the rate of fluid flow through the first and second valve portopenings 212, 214 and the valve 200. It should be noted that in thefirst embodiment, the rotor 246 is preferably configured to hold itsangular orientation and the position of the first and second disks 220,226 in the closed position relative to the valve port openings in thevalve housing 206.

It should be appreciated from the above that rotation of the firstmodulating disk 220 (which rotates the second pressure-responsive disk226) adjustably positions a wider or narrower portion of both the firstand second tapered semi-circular slots 222, 224 over the first andsecond valve port openings 212, 214, respectively, to adjustably varythe rate of fluid flow through the valve 200. When rotated to the closedposition, the second pressure-responsive disk 226 is configured tosealingly move against the second valve port opening 214 when pressurein the second valve port opening 214 is lower than that of the valvechamber 210 and first valve port opening 212, and is further configuredto move away from the second valve port opening 214 and cause the firstmodulating disk 220 to sealingly move against the first valve portopening 212 when pressure in the first valve port opening 212 is lowerthan that of the valve chamber 210 and second valve port opening 214, soas to provide an improved seal against the valve port opening having thelower pressure. Thus, the first and second disks 220, 226 of the secondembodiment provide for varying the fluid flow rate through the valve200, and also provide for improved closure in either flow directionagainst the valve port opening having the lower pressure therein.

It should be noted that any of the preceding exemplary embodiments,various features may be combined, substituted or omitted. Alternativeconstructions of one or more of the above exemplary embodiments mayinclude various combinations of the above disclosed features. Forexample, various alternate embodiments may include or omit either of thedisclosed check valve designs and bleed valve passage, and may furtherinclude or omit the biasing spring. Additionally, the above exemplaryembodiments may comprise various alternate constructions of themodulating member, in which various designs of a slot or groove havingvarying cross-sectional width may be employed to gradually change theeffective opening area through which fluid may flow through the valve.

Accordingly, the description of the various embodiments above is merelyexemplary in nature and, thus, variations that do not depart from thegist of the invention are intended to be within the scope of theinvention. Additional design considerations, such as the control of theapplication of voltage to the stepper motor, may be incorporated withoutdeparting from the spirit and scope of the invention. Such variationsare not to be regarded as a departure from the spirit and scope of theinvention. Accordingly, it is not intended that the invention be limitedby the particular embodiment or form described above, but by theappended claims.

In the above description, numerous specific details are set forth suchas examples of specific components, devices, methods, in order toprovide a thorough understanding of embodiments of the presentdisclosure. It will be apparent to a person of ordinary skill in the artthat these specific details need not be employed, and should not beconstrued to limit the scope of the disclosure. In the development ofany actual implementation, numerous implementation-specific decisionsmust be made to achieve the developer's specific goals, such ascompliance with system-related and business-related constraints. Such adevelopment effort might be complex and time consuming, but isnevertheless a routine undertaking of design, fabrication andmanufacture for those of ordinary skill.

Any dimensions provided herein are for purposes of illustration only asthe particular dimensions may vary depending on the particularapplication. The particular dimensions and values provided are notintended to limit the scope of the present disclosure.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”,“lower”, “above”, “upper”, “vertically,” “horizontally,” “inwardly,”“outwardly,” and the like may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures, and the disclosure is notnecessarily limited to such positions. Spatially relative terms may beintended to encompass different orientations of the device in use oroperation in addition to the orientation depicted in the figures. Forexample, if the device in the figures is turned over, elements describedas “below” or “beneath” other elements or features would then beoriented “above” the other elements or features. Thus, the example term“below” can encompass both an orientation of above and below. The devicemay be otherwise oriented (rotated 90 degrees or at other orientations)and the spatially relative descriptors used herein interpretedaccordingly.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The disclosure herein of particular values and particular ranges ofvalues for given parameters are not exclusive of other values and rangesof values that may be useful in one or more of the examples disclosedherein. Moreover, it is envisioned that any two particular values for aspecific parameter stated herein may define the endpoints of a range ofvalues that may be suitable for the given parameter. The disclosure of afirst value and a second value for a given parameter can be interpretedas disclosing that any value between the first and second values couldalso be employed for the given parameter. Similarly, it is envisionedthat disclosure of two or more ranges of values for a parameter (whethersuch ranges are nested, overlapping or distinct) subsume all possiblecombination of ranges for the value that might be claimed usingendpoints of the disclosed ranges.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

1. A reversible flow valve comprising: a valve chamber having a lowerwall with a first valve port opening and a second valve port opening incommunication with a first inlet/outlet and a second inlet/outlet,respectively; a shaft rotatably disposed in the valve chamber; an innermodulating disk rotatably coupled to the shaft, the inner modulatingdisk disposed in the valve chamber over the first valve port opening,and having a first opening aligned with the first valve port opening,where the inner modulating disk is configured to rotate from a closedposition in which the inner modulating disk is positioned over the firstvalve port opening, to an open position in which rotation of the innermodulating disk positions at least a portion of the first opening overthe first valve port opening, to thereby allow fluid flow through thefirst valve port opening and the first opening, the inner modulatingdisk being configured to be movable in an axial direction towards andaway from the first valve port opening; an outer modulating diskencircling the inner modulating disk, the outer modulating disk disposedin the valve chamber over the second valve port opening, and having asecond opening aligned with the second valve port opening, the outermodulating disk being configured to rotate with the inner modulatingdisk from a closed position, in which the outer modulating disk ispositioned over the second valve port opening, to an open position inwhich rotation of the outer modulating disk adjustably positions atleast a portion of the second opening over the second valve portopening, to thereby allow fluid flow through the second valve portopening and the second opening, the outer modulating disk beingconfigured to be movable in an axial direction towards and away from thesecond valve port opening; wherein the inner modulating disk in theclosed position is configured to move away from the first valve portopening, and the outer modulating disk in the closed position isconfigured to move against the second valve port opening, to therebyresist fluid flow through the second valve port opening; and wherein theouter modulating disk in the closed position is configured to move awayfrom the second valve port opening, and the inner modulating disk in theclosed position is configured to move against the first valve portopening, to thereby resist fluid flow through the first valve portopening.
 2. The valve of claim 1, wherein: the first opening of theinner modulating disk comprises a first tapered slot, such that rotationof the inner modulating disk adjustably positions a wider or narrowerportion of the first tapered slot over the first valve port opening, toadjustably vary the rate of fluid flow through the first valve portopening and the first tapered slot; and/or the second opening of theouter modulating disk comprises a second tapered slot, such thatrotation of the outer modulating disk adjustably positions a wider ornarrower portion of the second tapered slot over the second valve portopening, to adjustably vary the rate of fluid flow through the secondvalve port opening and the second tapered slot.
 3. The valve of claim 2,further comprising a motor coupled to the shaft for effecting rotationof the inner and outer modulating disks, wherein the motor is operablefor controllably rotating the inner and outer modulating disks toincrementally index the first and second tapered slots to a plurality ofpositions for incrementally adjusting the rate of fluid flow through thefirst and second valve port openings.
 4. The valve of claim 1: whereinthe inner modulating disk in the closed position is configured to moveaway from the first valve port opening by a fluid pressure in the firstinlet/outlet and first valve port opening that is higher than the fluidpressure in the second inlet/outlet, to communicate said higher fluidpressure to the valve chamber, and the outer modulating disk in theclosed position is configured to be pushed against the second valve portopening by a fluid pressure in the valve chamber that is higher than thefluid pressure in the second valve port opening, to thereby resist fluidflow through the second valve port opening; and wherein the outermodulating disk in the closed position is configured to move away fromthe second valve port opening by a fluid pressure in the secondinlet/outlet and second valve port opening that is higher than the fluidpressure in the first inlet/outlet, to communicate said higher fluidpressure to the valve chamber, and the inner modulating disk in theclosed position is configured to be pushed against the first valve portopening by a fluid pressure in the valve chamber that is higher than thefluid pressure in the first valve port opening, to thereby resist fluidflow through the first valve port opening.
 5. The valve of claim 1,further comprising: a first biasing spring for biasing the innermodulating disk towards the first valve port opening; a second biasingspring for biasing the outer modulating disk towards the second valveport opening; whereby the inner modulating disk in its closed positionis configured to be moved away from the first valve port opening againstthe force of the first biasing spring by a fluid pressure in the firstvalve port opening that is greater than fluid pressure in the valvechamber; and whereby the outer modulating disk in its closed position isconfigured to be moved away from the second valve port opening againstthe force of the second biasing spring by a fluid pressure in the secondvalve port opening that is greater than fluid pressure in the valvechamber.
 6. The valve of claim 1, wherein: the shaft is configured to bemovable in an axial direction such that the inner modulating diskcoupled to the shaft is movable in a direction towards and away from thefirst valve port opening; fluid pressure in the first valve port openingthat is higher than fluid pressure in the valve chamber causes the innermodulating disk in its closed position to move in an axial directionaway from the first valve port opening; and fluid pressure in the firstvalve port opening that is lower than fluid pressure in the valvechamber causes the inner modulating disk in its closed position to movein an axial direction against the first valve port opening.
 7. The valveof claim 1, wherein: the inner modulating disk comprises a plate havinga generally round contour and a central aperture having a keyedconfiguration; the first opening comprises a first tapered semi-circularslot concentric with the central aperture; the outer modulating diskcomprises a plate having a generally ring-shaped contour; and the secondopening comprises a second tapered semi-circular slot concentric withthe first tapered semi-circular slot.
 8. The valve of claim 7, wherein:the outer modulating disk is coupled to the inner modulating disk suchthat the first and second tapered semi-circular slots are positioned ongenerally opposing sides of the central aperture; and the inner andouter modulating disks are coupled by a key and slot arrangement thatpermits the outer modulating disk to move axially relative to the innermodulating disk.
 9. A reversible flow valve comprising: a valve housinghaving a valve chamber including a first valve port opening and a secondvalve port opening in communication with a first inlet/outlet and asecond inlet/outlet, respectively; a shaft rotatably disposed in thevalve chamber; a first valve plate disposed in the valve chamber overthe first valve port opening and rotatably coupled to the shaft, thefirst valve plate having a first opening positioned in the first valveplate so as to align with the first valve port opening, where the firstvalve plate is configured to rotate from a closed position, in which thefirst valve plate is positioned over the first valve port opening, to anopen position in which rotation of the first valve plate positions atleast a portion of the first opening over the first valve port opening,to thereby allow fluid flow through the first valve port opening and thefirst opening, wherein the first valve plate in its closed position isconfigured to be movable in an axial direction towards and away from thefirst valve port opening; and a second valve plate that is configured torotate with the first valve plate, the second valve plate beingconfigured to cover the second valve port opening when the first valveplate is rotated to the closed position, wherein the second valve platein its closed position is configured to be movable relative to the firstvalve plate in an axial direction towards and away from the second valveport opening; wherein the first valve plate in the closed position isconfigured to move away from the first valve port opening, and thesecond valve plate in the closed position is configured to move againstthe second valve port opening, to thereby resist fluid flow through thesecond valve port opening; and wherein the second valve plate in theclosed position is configured to move away from the second valve portopening, and the first valve plate in the closed position is configuredto move against the first valve port opening, to thereby resist fluidflow through the first valve port opening.
 10. The valve of claim 9,wherein: the first valve plate comprises a plate having a generallyround contour, a central aperture having a keyed configuration, and acavity therein; the first opening comprises a first taperedsemi-circular slot concentric with the aperture and a second taperedsemi-circular slot concentric with the first tapered semi-circular slot;and the second valve plate is disposed within the cavity in the firstvalve plate;
 11. The valve of claim 10, wherein the second valve platecomprises a plate having a generally disk shaped contour and a generallyconvex-shaped upper surface, said second valve plate being smaller thanthe cavity of the first valve plate such that the second valve plate ismovable within the cavity in an axial direction relative to the firstvalve plate.
 12. The valve of claim 9, further comprising a motorcoupled to the shaft for effecting rotation of the first and secondvalve plates, wherein the motor is operable for controllably rotatingthe first and second valve plates.
 13. The valve of claim 9, wherein thefirst opening of the first valve plate comprises a first taperedsemi-circular slot positioned so as to align with the first valve portopening; and a second tapered semi-circular slot concentric with thefirst tapered semi-circular slot, and positioned so as to align with thesecond valve port opening; whereby the first valve plate is configuredto rotate from a closed position to an open position in which rotationof the first valve plate adjustably positions a wider or narrowerportion of the first and second tapered semi-circular slots over therespective first and second valve port openings, such that fluid flowrate through the valve is controllable by the rotational positioning ofa wider or narrower portion of the first and second taperedsemi-circular slots over the respective first and second valve portopenings.
 14. The valve of claim 9: wherein the first valve plate in theclosed position is configured to move away from the first valve portopening by a fluid pressure in the first inlet/outlet and first valveport opening that is higher than the fluid pressure in the secondinlet/outlet, to communicate said higher fluid pressure to the valvechamber; and the second valve plate in the closed position is configuredto be pushed against the second valve port opening by a fluid pressurein the valve chamber that is higher than the fluid pressure in thesecond valve port opening, to thereby resist fluid flow through thesecond valve port opening; and wherein the second valve plate in theclosed position is configured to move away from the second valve portopening by a fluid pressure in the second inlet/outlet and second valveport opening that is higher than the fluid pressure in the firstinlet/outlet, to communicate said higher fluid pressure to the valvechamber; and the first valve plate in the closed position is configuredto be pushed against the first valve port opening by a fluid pressure inthe valve chamber that is higher than the fluid pressure in the firstvalve port opening, to thereby resist fluid flow through the first valveport opening.
 15. The valve of claim 9, wherein the shaft is configuredto be movable in an axial direction such that the first valve platecoupled to the shaft is movable in a direction towards and away from thefirst valve port opening.
 16. The valve of claim 9, wherein: the firstvalve plate comprises a plate having a generally round contour and acentral aperture having a keyed configuration; the first opening of thefirst valve plate comprises a first tapered semi-circular slotconcentric with the aperture; the second valve plate comprises a platehaving a generally ring-shaped contour and a second taperedsemi-circular slot concentric with the first tapered semi-circular slot;and the second valve plate is coupled to the first valve plate such thatthe first and second tapered semi-circular slots are positioned ongenerally opposing sides of the central aperture and such that thesecond valve plate is movable axially relative to the first valve plate.17. The valve of claim 9, wherein: the first valve plate includes acavity therein; and the second valve plate comprises a plate disposedwithin the cavity and having a generally disk shaped contour and agenerally convex-shaped upper surface, said second valve plate beingsmaller than the cavity of the first valve plate such that the secondvalve plate is movable within the cavity in an axial direction relativeto the first valve plate.
 18. The valve of claim 9, wherein: the firstvalve plate is configured to move away from the first valve port openingto communicate fluid pressure through a first bleed passage to the valvechamber, which fluid pressure pushes the second valve plate into sealingengagement with the second valve port opening and restricts fluid flowthrough the second valve port opening; and the second valve plate isconfigured to move away from the second valve port opening tocommunicate fluid pressure through a second bleed passage to the valvechamber, which fluid pressure pushes the first valve plate into sealingengagement with the first valve port opening and restricts fluid flowthrough the first valve port opening.
 19. A valve comprising: a valvechamber having a lower wall with a first valve port opening and a secondvalve port opening in communication with a first inlet/outlet and asecond inlet/outlet, respectively; a shaft rotatably disposed in thevalve chamber; a first valve plate disposed in the valve chamber overthe first and second valve port openings and rotatably coupled to theshaft, the first valve plate being configured to be movable in an axialdirection towards and away from the first and second valve portopenings, said first valve plate having a first opening positioned so asto align with the first valve port opening, and a second opening andcavity positioned therein so as to align with the second valve portopening, where the first valve plate is configured to rotate from aclosed position, in which the first valve plate is positioned over thefirst valve port opening and the cavity is positioned over the secondvalve port opening, to an open position in which rotation of the firstvalve plate positions at least a portion of the first opening over thefirst valve port opening and at least a portion of the second openingover the second valve port opening, for adjustably varying the fluidflow rate through the valve; a second valve plate disposed within thecavity in the first valve plate, so as to be positioned over the secondvalve port opening when the first valve plate is rotated to the closedposition, the second valve plate being configured to be movable relativeto the first valve plate in an axial direction towards and away from thesecond valve port opening; wherein the first valve plate in the closedposition is configured to move away from the first valve port opening,and the second valve plate in the closed position is configured to moveagainst the second valve port opening, to thereby resist fluid flowthrough the second valve port opening; and wherein the second valveplate in the closed position is configured to move away from the secondvalve port opening, and the first valve plate in the closed position isconfigured to move against the first valve port opening, to therebyresist fluid flow through the first valve port opening.
 20. The valve ofclaim 19, wherein: the first opening of the first valve plate comprisesa first tapered slot; and/or the second opening of the first valve platecomprises a second tapered slot; and/or the second valve comprises aplate having a generally disk shaped contour and a generallyconvex-shaped upper surface, said second valve plate being smaller thanthe cavity of the first valve plate such that the second valve plate isconfigured to move within the cavity in an axial direction relative tothe first valve plate; and/or the shaft is configured to be movable inan axial direction such that the first valve plate coupled to the shaftis movable in a direction towards and away from the first valve portopening; and/or a motor is coupled to the shaft for controllablyrotating the first and second valve plates to incrementally adjust therate of fluid flow through the first and second valve port openings.